A replication-defective bivalent adenovirus-vectored vaccine provides robust and durable protection against both canine distemper virus and canine parvovirus.

Canine distemper virus (CDV) and canine parvovirus (CPV) are highly contagious and often fatal pathogens in dogs. Current live-attenuated vaccines, while effective, carry the risk of virulence reversion. This study aimed to develop a safer, replication-defective bivalent vaccine using an adenovirus vector to simultaneously protect against both CDV and CPV. The recombinant vaccine, designated Ad5-(VP2 +H), was engineered to coexpress the CDV hemagglutinin (H) protein (CDV-H) and the CPV Viral Protein 2 (CPV-VP2). Its immunogenicity and protective efficacy were evaluated in mouse and canine models. The results demonstrated that Ad5-(VP2 +H) elicited a potent and durable antigen-specific immune response. Furthermore, compared with a commercially available live attenuated vaccine, the Ad5-(VP2 +H) candidate exhibited a superior safety profile. In conclusion, the adenovirus-vectored Ad5-(VP2 +H) vaccine is a promising and safer alternative for the simultaneous prevention of CDV and CPV in dogs. This approach addresses the key limitation of traditional live-attenuated vaccines by eliminating the risk of virulence reversion while providing effective immunity.